Insulated carbon body



Feb. 5, 1946. O coN 2,394,041

INSULATED CARBON BODY Filed July 8, 1940 INVENTOR OTTMAR Com/M071ATTORNEY.

ing drawing in which:

Patented Feb. 5, 1942;

INSULATED CARBON BODY Ottmar Conradty,

Germany; vested dian Rothenbach on the Pegnitl, in the Alien PropertyCusto- Application July 8, 1940, Serial No. 344,455 In Germany June 30,1939 1 Claim.

This invention relates to artificial carbon bodies including aninsulating support for mounting.

In variou branches of the electrotechnical industry, carbon bodies arerequired which either have to be insulated from each other or fromanother part of a machine or apparatus, such articles being, forexample, carbon collectors and carbon slip rings as well as other carboncontacts operating under high electrical load and reaching high workingtemperature. The conventional insulating materials, such as, cement, aredestroyed and decomposed at the high temperatures in question, moreparticularly by function of electric sparks, and converted into electricconductors, whereby they become useless as electric insulators andmechanical supports for the carbon bodies.

It is an important object of the present invention to provide a carbonbody and insulator unit the insulation of which is capable of resistingextreme electric and heat stresses.

with this and further objects in view, as may become apparent from thewithin disclosures, the invention consists not only in the structuresherein pointed out and illustrated by the drawings, but includes furtherstructures coming within the scope of what hereinafter may be claimed.

The character of the invention, however, may be best understood breference to certain of its structural forms, as illustrated by theaccompany- Fig. 1 is a side elevation of a carbon and insulator unithaving theinvention applied thereto.

Fig. 2 is an end view of Fig. 1.

Fig. 3 is an axial section of Fig. 1. a

Similar referencenumerals denote similar parts inthe difl'erent figures.y 1

Referring now to the drawing in greater-detail.

An annular carbon body 5 is mounted on a tubular insulating body 6.Buffer materials I, consisting, for instance, of asbestos or slag wool,may be provided between the carbon body and the collars B of theinsulating body adjacent thereto, in order that mechanical shrinkingtensions caused by the cooling down of theinsulating body may not betransferred upon the carbon material.

The manufacturing process will now be described.

I apply the insulating material on the carbon body under action of heat(l000-l400 C.) in a burning, baking or casting operation, using gas as afuel. I have found that an insulating material which can be subjected toa treatment of this kind will resist also the stresses occurring inworking order by sparking and hea Various insulating materials may beused which can be applied by heat. Depending on the kind oi! insulatingmaterial the same is applied on the carbon before the same has beenburnt, or after the preliminary baking or firing or after the hardeningor final baking.

It is then hardened and solidified by heat. Where the insulatingmaterial is applied on the carbon before the burning or before thehardening-on, the carbon will be hardened-on during the heat treatmentof the insulating material; On the other hand, where the carbon has beenfull annealed already, it will undergo a second annealing process withthe insulating material applied thereon. This is by no meansobjectionable, but on the contrary the properties of the carbon may bemodified by the second baking processin any desired manner.

In the practice of my invention, I may for instance roduce a carbon bodyin known manner by compression, then I press a ceramic insulatingmaterial, for instance, steatite (magnesium and aluminum silicate),around the carbon body, using a suitable mold and finally the compositebody obtained by pressing together the two parts is subjected to acommon burning or' baking process. It will be appreciated that theshrinking characteristics of the two substances which are being usedhave to be matched with each other in a suitable manner. Where largedifferences are existing in the shrinkage of the two materials, namely,carbon and insulator, the compressed carbon may be pre-baked to suchadegree, that in the common final annealingprocess (hardening-on) it doesnot shrink more than the insulating material pressed around it after theprebaking or first annealing. Again, the ceramic insulating body may befirst shaped and pre-annealed, then united with the hardened-on carbonand then the whole unit may be annealed once more up to the temperaturecausing maximum shrinkage of the insulating body.

According to a further feature of the invention, the insulating body mayconsist of vitreous substances, more particularly, glass, which is castor die-cast upon or around the suitably formed carbon body in a moltenand liquid condition. In the same manner, any smelting fiux of the glassor enamel type or smeltable blast furnace slag may be applied.

According to another feature of the invention, I may use a ceramicmaterial which contains suitable flux or frit admixtures and thereforedoes not require a real burning process but is pressed around the carbonbody in powdered form and then subjected merely to a sintering processwhich may consist in the simultaneous applies-- tion or pressure andheat Substances which may be slntered in this manner, are, for instance,glass dust, and slag meal. The solidification of the insulating materialby a sintering operation without pressure or with simultaneousapplication of pressure oilers the advantage that the difi'erences ofexpansion or shrinkage oi the two materials are less than with aconventional ce ramic process. In most instances, it will be advantageous to provide bolsters, as at I mm. 3, between the carbon andinsulating material, to compensate the considerable pressures due toshrinkage of the insulating material.

The method of the present invention has been described in detail withreference to specific embodiments. It is to be understood, however, thatthe invention is not limited by such specific reierence but is broaderin scope and capable of scribed and illustrated in the drawing.

other embodiments than those specifically dem It is also to beunderstood that the following claim is intended to cover all of thegeneric and specific ieatures oi the invention herein described, and allstatements or the scope oi the invention which, as a matter of language,might be said to fall therebetween.

I claim:

A composite body comprising a substantially cylindrical portion oiinsulating material having an annular peripheral recess therein on itsouter surface, an annular carbon body fitting in said recess andcontacting the bottom of the latter, the thickness of said body beingless than the width 01 the recess, and a bolster oi refractoryinsulating material disposed between at least one 01 the recesssidewalls and the proximate side of the body.

OT'I'MAR CONRAUI'Y.

